1. Field of the Invention
This invention relates to a spray-dried layer silicate/sodium sulfate agglomerate which is suitable as a constituent of solid, free-flowing detergent and cleaning preparations and which, by virtue of its porosity, is capable of taking up additional liquid constituents of detergent and cleaning preparations.
For a variety of reasons, certain constituents of solid, free-flowing detergent and cleaning preparations are unsuitable for spray-drying which is the most widely used process in detergent manufacture. Oxygen-releasing compounds tend to decompose prematurely at the high temperatures prevailing during spray drying. Other constituents, such as enzyme preparations for example, lose their activity under the spray drying conditions. Yet other constituents, for example nonionic surfactants, are removed from the detergent mixture with the evaporating water during spray drying and are thus lost to the dried detergent. The same applies to perfumes. Accordingly, those constituents which may be spray-dried without difficulty are generally spray-dried, while detergent constituents which cannot be spray-dried for the reasons explained above are optionally added to this primary product in another detergent manufacturing step. In many cases, however, the incorporation of liquid nonionic surfactants in relatively large quantities as a detergent constituent in a substantially dried, free-flowing product presents a problem. The uniformity of distribution of this liquid component to be added in relatively large quantities to the spray-dried primary product has to meet stringent requirements.
2. Discussion of Related Art
Earlier-filed European patent application 86/109717.8 describes layer silicates having a smectite-like crystal structure, but in comparative terms, a distinctly reduced swelling power in water. These layer silicates are synthetic, finely-divided, water-insoluble layer silicates which have a smectite-like crystal phase, but have increased contents of bound alkali metal and silicate and, compared with pure layer silicates of this type, a distinctly reduced swelling power in aqueous suspension and which have the following oxide summation formula EQU MgO.multidot.a M.sub.2 O.multidot.b Al.sub.2 O.sub.3 .multidot.c SiO.sub.2 .multidot.n H.sub.2 O
wherein M represents sodium or a mixture of sodium and lithium, with the proviso that the molar ratio of sodium to lithium is at least 2, and wherein the parameters a, b, c and n each represent a number within the following ranges:
a is equal to 0.05 to 0.4, PA1 b is equal to 0 to 0.3, PA1 c is equal to 1.2 to 2.0, and PA1 n is equal to 0.3 to 3.0. PA1 x is equal to 0 to 0.3, preferably 0 to 0.1; PA1 y is equal to 0 to 0.5, preferably 0 to 0.4; PA1 x+y is equal to 0.1 to 0.5, preferably 0.2 to 0.4; PA1 z is equal to 1 to 22, preferable 1 to 14; PA1 m is equal to 0.1 to 0.5, preferably 0.1 to 0.3; and PA1 n is equal to 0 to 8, preferably 2 to 6.
In this oxide summation formula, the water content n H.sub.2 O represents the water bound in the crystal phase. These very finely-divided clay minerals may be regarded as layer silicates having structural features of mica-like layer silicates, albeit with a dislocation in regard to the linkage of adjacent layers. A structural formula of the type usually expressed in idealized form for clay minerals can only be drawn up under additional hypotheses for the layer silicates according to the invention. However, the chemical composition of the new compounds shows more Na.sub.2 O and SiO.sub.2 than the associated saponite and hectorite smectite. It may be assumed that, in addition to the layer arrangement typical of mica-like compounds of this type, these layer silicates contain units of incorporated sodium silicates. From the viewpoint of structure and synthesis, the crystallization of the layer silicates may presumably be interpreted as a mixed crystal formation in which sodium silicate is incorporated in smectite. The X-ray diffractograms show that this incorporation is not regular, but instead leads to dislocations in the crystallites. Accordingly, crystallographic characterization by lattice constants which describe an elementary cell is not possible. On the basis of the chemical composition selected, synthetic smectites as defined above include saponite- and hectorite-like phases. The mixed crystal system should therefore be described by the following structural formula EQU [Na.sub.x+y (Mg.sub.3-x Li.sub.x)(Si.sub.4-y Al.sub.6)O.sub.10 (OH).sub.2 ].multidot.m [Na.sub.2 Si.sub.z O.sub.2z+1 ].multidot.n H.sub.2 O
the first part of the formula characterizing the smectite, and the second part the sodium polysilicate. both components form one phase in which the smectite determines the structure.
The variables may assume the following numerical values:
The composition of the synthetic layer silicates according to the invention which differs distinctly from the pure smectites and the associated dislocation in the crystal structure leads to changes in a number of properties typical of layer silicates per se, particularly in regard to their swellability and hence their gel-forming properties and also in their exchange capacity.
These layer silicates have an incrustation-inhibiting effect in detergents having a standard composition. In contrast to layer silicates of the smectite type, these synthetic layer silicates have no fabric softening power or no pronounced softening power. By virtue of its incrustation-inhibiting effect, this synthetic layer silicate, the production of which is described in the earlier-filed European patent application cited above, is a valuable constituent of modern detergent and cleaning preparations, all the more so as both the softening smectite clays and also the alkali metal aluminosilicates of the zeolite A type described as hosphate substitutes are water-insoluble detergent constituents which can lead to fabric incrustation under certain conditions. Such fabric incrustation can be effectively suppressed by the synthetic layer silicates described in the earlier-filed European patent application. In their production by the process described in the earlier-filed European patent application cited above, the synthetic layer silicates accumulate in the form of an aqueous suspension of a mixture of layer silicate and sodium sulfate. Although the sodium sulfate can be separated from the layer silicate by washing out the layer silicate filtered off, it is best, because sodium sulfate itself is a detergent constituent present in most detergents, to further process the layer silicate/sodium sulfate mixture during the production of detergent and cleaning preparations. The further processing of the layer silicates containing sodium sulfate together with most of the other detergent constituents is already described in the earlier-filed European patent application cited above. Accordingly, the disclosure of that European patent application is also specifically made part of the disclosure of the present application.
The processing of the mixture of sodium sulfate and synthetic layer silicate to layer silicate/sodium sulfate agglomerates and, optionally, their further processing for free-flowing detergent and cleaning preparations has never been described hitherto. Accordingly, the problem solved by the present invention is to provide layer silicate/sodium sulfate agglomerates in which the layer silicate is the synthetic layer silicate mentioned above.